Question: Simplify the following expression: $r = \dfrac{-7}{8n} - \dfrac{-9}{8n}$
Solution: Since the expressions have the same denominator we simply combine the numerators: $r = \dfrac{-7 - (-9)}{8n}$ Combine like terms: $r = \dfrac{2}{8n}$ Simplify by dividing numerator and denominator by 2: $r = \dfrac{1}{4n}$